ZMean2Test Command
 ZMean2Test( <List of Sample Data 1>, <σ1>, <List of Sample Data 2>, <σ2>, <Tail> )

Performs a Z test of the difference between two population means using the given lists of sample data and the population standard deviations. Tail has possible values "<", ">" , "≠" that determine the following alternative hypotheses:
"<" = difference in population means < 0
">" = difference in population means > 0
"≠" = difference in population means ≠ 0
Results are returned in list form as {Probability value, Z test statistic}.
 ZMean2Test( <Sample Mean 1 >, <σ1>, <Sample Size 1>, <Sample Mean 2 >, <σ2>, <Sample Size 2>, <Tail> )

Performs a Z test of the difference between two population means using the given sample statistics and population standard deviations. Tail is defined as above.